Theroux was educated for a couple of years at Allfarthing Primary School then moved to Westminster School (where he was a friend and contemporary of the comedians Adam Buxton and Joe Cornish). Another of his contemporaries was Liberal Democrat politician and current Deputy Prime Minister, Nick Clegg, with whom he travelled to America.[6] He then went to Magdalen College, Oxford, where he gained a first class degree in history and was noted for his film reviews for the Grapevine magazine.

Louis Theroux spends time with a small and very committed subculture of ultra-nationalist Jewish settlers. He discovers a group of people who consider it their religious and political obligation to populate some of the most sensitive and disputed areas of the West Bank, especially those with a spiritual significance dating back to the Bible.

Throughout his journey, Louis gets close to the people most involved with driving the extreme end of the Jewish settler movement.

In Weird Weekends (1998–2000), Theroux followed marginal, mostly American subcultures like survivalists, black nationalists, white supremacists and porn stars, often by living among or close to the people involved. Often, his documentary method subtly exposed the contradictions or farcical elements of some seriously held beliefs. Theroux himself describes the aim of the series as: "Setting out to discover the genuinely odd in the most ordinary setting. To me, it's almost a privilege to be welcomed into these communities and to shine a light on them and, maybe, through my enthusiasm, to get people to reveal more of themselves than they may have intended. The show is laughing at me, adrift in their world, as much as at them. I don't have to play up that stuff. I'm not a matinee idol disguised as a nerd." Despite calls for a complete DVD set of the Weird Weekends series, only selected episodes have ever been available for purchase.

In When Louis Met... (2000–02), Theroux accompanied a different British celebrity in each programme as they go about their day-to-day business, interviewing them about their lives and experiences as he did so. His episode about British entertainer Jimmy Savile, When Louis Met Jimmy, was voted one of the top fifty documentaries of all time in a survey by Britain's Channel 4. In When Louis Met the Hamiltons, the disgraced ToryMPNeil Hamilton and his wife Christine were arrested following false allegations of indecent assault during the course of filming.

In When Louis Met Max Clifford, Max Clifford tried to set Louis up. However, it backfired when Clifford was caught lying, as the crew was still recording his live microphone during the conversations. After this series concluded, a retrospective was aired called Life with Louis. He was meant to do a similar programme with Michael Jackson before Martin Bashir completed his documentary for ITV, but it was cancelled.[citation needed] Theroux went on to make a documentary called Louis, Martin & Michael about his quest to get an interview with Michael Jackson. Selected episodes of When Louis Met... were included as bonus content on a Best-Of collection of Weird Weekends. The entire series has never been released on DVD.

In these special programmes, beginning in 2003, Theroux returned to American themes, working at feature-length, this time with a more natural tone. In March 2006, he signed a new deal with the BBC to make 10 films over the course of three years.[7] Subjects for the specials include criminal gangs in Lagos, Neo-Nazis in America, ultra-Zionists in Israel, child psychiatry and the prison system in California and Florida. A 2007 special, The Most Hated Family in America, received strong critical praise from the international media.

As part of the Weird Weekends episode Porn, he agreed to a cameo in the 1997 gay pornography release Take a Peak.[8] He did not perform sexual acts in the film, but made a brief appearance as a ranger in search of a criminal.

In the Weird Weekends episode on Infomercials he was featured as a live-salesman for an at-home paper shredder for the Home Shopping Network.[9]

He used to live in the London district of Harlesden.[1][10] He now lives in Los Angeles, after moving there in early 2013 with his family.[11] As of mid-2014 his Twitter status states he now, again, lives in Britain.[12]

In a 2012 masterclass, Theroux spoke of the challenges of combining family life with the need to go away to work on projects.[13]